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A  Study  of  Handedness 

By 

W.  FRANKLIN  JONES,  Ph.  D. 

Head  of  Department  of  Education 

and  Diredtor  of  Graduate  Courses 

University  of  South  Dakota 


Price  35  cents,  prepaid 


EQUIPMENT     OR  DETERMINING  HANDEDNESS. 

In  order  to  r     ^,       ;  demands  of  school  officials,  physicians 


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A  Study  of  Handedness 

By 

W.  FRANKLIN  JONES,  Ph.  D. 

Head  of  Department  of  Education 

and  Direc5tor  of  Graduate  Courses 

University  of  South  Dakota 


Price  35  cents,  prepaid 


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A  STUDY  OF  HANDEDNESS. 

The  left  handed  child  has  been  an  educational  bone  of 
contention.  Tradition  has  decreed  that  left  handedness  is 
only  individual  habit,  and  so  its  followers  have  set  to  work 
industriously  to  transform  all  left  handers  into  right  hand- 
ers.  Many  cases  of  left  handedness  have  apparently  disap- 
peared under  this  treatment,  and  thus  on  the  surface,  at 
least,  tradition  has  been  justified.  Only  here  and  there  has 
been  found  a  child  so  stubbornly  left  handed  that  no  train- 
ing, however  persistent,  has  been  quite  able  to  transfer  him 
to  the  right  hand  and  arm ;  and  it  is  this  little  group  of  sur- 
vivors that  has  set  many  an  investigator  to  work  on  the 
problem  of  handedness. 

On  the  other  hand,  there  have  been  those  v/ho,  after 
more  or  less  careful  study,  have  maintained  that  left  handed- 
ness is  a  born  trait,  and  that  no  parent  or  teacher  should  as- 
sume to  interfere  with  nature's  process.  They  have  pointed 
out  that  the  majority  of  the  human  race  is  undoubtedly 
right  handed  born,  but  that  there  is  a  respectable  minority 
that  is  left  handed  born;  yet  the  evidence  on  which  these 
claims  have  been  based  has  been  without  scientific  proof,  and 
the  proportion  of  born  right  and  and  born  left  handed  indi- 
viduals has  not  been  established,  indeed  can  not  be  estab- 
lished until  some  reliable  means  have  been  devised  for  dis- 
tinguishing bom  handedness  from  acquired  hanfledness. 
Gould,  Cunningham,  Jackson  and  others  have  made  many 
shrewd  observations  that  give  some  ground  for  their  claims, 
and  Biervliet  and  Baldwin  are  to  be  given  credit  for  having 
given  us  the  first  scientific  data;  but  we  need  further  evi- 
dence if  the  foregoing  controversies  are  to  be  settled. 

Finally,  we  find  a  third  class  of  students  who  reason 
from  bilateral  symmetry  to  ambidexterity.  "Two  equal 
arms"  is  their  creed,  and  it  has  filled  England  with  ambidex- 
terity societies.  These  societies  seem  to  feel  called  upon  to 
rescue  the  race  from  "one  sided  development."  That  their 
studies  and  their  teachings  have  been  both  industrious  and 
heroic  is  shown  by  the  fact  that  their  opponents  have  called 
them  "ambidexterity  cranks."  They,  too,  have  given  us  lit- 
tle evidence. 


4    /  A  STUDY  OF  HANDEDNESS 

It  is  clear  that  opinion  will  never  settle  these,  any  more 
than  it  has  settled  other,  controversies;  and  we  shall  con- 
tinue variously  to  treat  and  perhaps  to  mistreat  the  left 
handed  child,  both  in  home  and  in  school,  until  we  know  him 
better. 

Then,  too,  if  we  err  because  we  do  not  understand  left 
handedness,  shall  we  say  we  are  certain  of  our  deahngs  with 
right  handedness?  If  a  child  is  bom  with  a  major  and  a 
minor  arm,  may  he  not  more  or  less  hopelessly  injure  the 
major  arm  and  so  be  forced  to  adopt  the  minor  arm?  May 
an  injury  to  the  major  arm  early  in  life  shift  the  child  over 
to  the  minor  arm,  unknown  to  parents,  and  thus  send  the 
child  through  life  mistaken  as  to  his  own  birthright  of  hands 
and  arms  ?  If  it  is  really  possible  to  transfer  from  one  arm 
to  the  other  by  accident,  then  how  is  any  one  to  know  wheth- 
er he  is  actually  born  right  or  left  ?  If  we  could  but  discover 
some  scientific  means,  some  measures  or  scales,  for  deter- 
mining both  born  handedness  and  adopted  handedness,  then 
we  could  answer  these  questions. 

Other  questions  arise.  If  an  individual  is  transferred 
from  the  major  to  the  minor  arm,  either  by  accident  or  by 
purposive  interference,  what  are  the  consequences?  Are 
the  possibilities  of  the  minor  arm  minor  possibilities  as  com- 
pared with  those  of  the  major  arm?  Does  hand  transfer 
mean  ultimate  loss  of  hand  skill  ?  and  does  this  interference, 
whether  accidental  or  purposive,  bring  physiological  disas- 
ter? If,  again,  we  had  reliable  means  of  determining  both 
born  handedness  and  adopted  handedness,  we  could  apply 
tests  of  hand  skill  to  right  handers,  left  banders,  and  trans- 
fers, and  thus  discover  by  experiment  the  consequence  of 
transfer  in  terms  of  hand  and  arm  skill;  and  this  in  turn 
might  pave  the  way  to  a  study  of  physiological  consequences 
attending  hand-transfer. 

It  was  in  the  hope  of  discovering  some  means,  some 
measures,  or  scales,  that  could  make  it  possible  to  proceed 
with  a  scientific  handling  of  the  problems  of  handedness 
that  this  investigation  was  started  and  carried  on  for  ten 
years.  Re-stated  for  the  sake  of  clearness,  this  investiga- 
tion deals  with  the  following  multiple  problem. 


THE  PROBLEM  STATED. 

Part  I.  (1)  HOW  CAN  WE  DETERMINE,  de  novo, 
WHETHER  A  CHILD  IS  BORN  RIGHT  OR  LEFT  HAND- 
ED V  (2)  HOW  CAN  WE  DISTINGUISH  BORN  HANDED- 
NESS FROM  ACQUIRED  HANDEDNESS? 

Part  II.  SHOULD  THE  LEFT  HANDED  CHILD  BE 
TRANSFERRED  TO  THE  RIGHT  HAND? 


MATERIAL  AND  HANDLING. 

The  material  used  in  this  investigation  consists  of  the 
following  measures  taken  of  each  arm  of  twenty  thousand 
individuals  ranging  in  ages  from  stillborn  to  centenarian : 

1.  Length  of  the  ulna-plus  (the  ulna  plus  the  hand  to 
the  middle  knuckle  of  the  little  finger) . 

2.  Circumference  of  the  palm. 

3.  Circumference  of  the  wrist. 

4.  Length  of  the  humerus. 

5.  Circumference  of  the  forearm  relaxed. 

6.  Circumference  of  the  forearm  contracted. 

7.  Circumference  of  the  ami  relaxed. 

8.  Circumference  of  the  arm  contracted. 
Additional  material  was  derived  by  taking  measures  of 

the  bones  of  the  arms  of  a  dozen  cadavers,  and  of  a  dozen 
unpieced  human  skeletons. 

The  Brachiometer. 

To  facilitate  the  work,  a  simple  instrument  (called 
"brachiometer")  was  devised  to  give  exact  and  correspond- 
ing measures  of  the  two  arms.  It  is  shown  in  the  cut  that 
follows.  It  is  made  of  hard  wood,  with  working  parts  of 
brass.  The  base  of  the  instrument  is  2i/t  by  6  inches ;  and 
the  upright,  bearing  the  measuring  scale,  the  sliding  indi- 
cator, and  the  metallic  arm  cuff,  is  18  inches  in  length.  The 
arm  cuff  is  a  brass  band,  in  two  parts,  each  part  secured  to 
the  upright  and  hinged  so  as  to  make  it  adjustable  to  arms 
of  varying  sizes. 

The  Measuring  Details. 

1.  Ulna-plus. — In  taking  the  ulna-plus  the  brachiome- 
ter was  usually  placed  on  a  low  table  at  which  the  subject 
was  seated.  (The  measures  may  be  taken  with  the  subject 
standing ;  but  if  a  table  is  used  it  must  be  low  enough  to  give 
an  acute  angle  at  the  elbow.)  The  bared  arm  was  placed 
with  the  point  of  the  elbow  pressing  firnily  downward  on  the 
base  of  the  brachiometer  and  the  arm  extending  along  the 


MEASURING   THE   ULNA-PLUS 


8  A  STUDY  OF  HANDEDNESS 

upright  measuring-  scale.  The  foreami,  hand,  and  lower  joint 
of  the  Httle  finger  were  carefully  held  in  a  straight  line,  with 
the  little  finger  bent  at  right  angle  at  the  middle  knuckle. 
(Practice  in  placing  and  straightening  the  arm  is  required 
to  give  reliable  measures.)  The  length  of  the  ulna-plus  was 
then  found  by  sliding  the  indicator  down  the  scale  until  it 
rested  on  the  exposed  middle  knuckle  of  the  little  finger,  the 
reading  being  taken  on  the  scale  just  under  the  indicator. 
(The  length  of  the  ulna-plus  is  taken,  rather  than  the  length 
of  the  ulna,  for  the  reason  that  the  former  is  far  more 
readily  derived,  as  may  be  seen  by  trial.) 

2.  Circumferences  of  Forearm. — Without  removing 
the  arm  from  the  brachiometer,  the  halves  of  the  metal  cuff 
were  pressed  against  th«  forearm  and  a  pencil  line  drawn  on 
each  side  of  the  bare  forearm  along  the  lower  edge  (along 
the  upper  edge  with  a  long  arm)  of  the  metal  cuff.  The 
brachiometer  was  then  removed,  and  with  the  arm  held  in 
the  same  position  as  when  marked,  the  circumference  of  the 
"forearm  relaxed"  was  found  by  measuring  to  the  pencil 
lines  with  a  narrow  and  flexible  tape  (anthropometric  tape) 
snugly  drawn.  (Practice  is  required  to  enable  the  operator 
to  draw  the  tape  at  constant  tension.)  Then,  without  re- 
moving the  tape,  a  pencil  was  slipped  into  the  hand  of  the 
arm  being  measured  and  the  subject  was  instructed  to  grip 
the  pencil  three  times  with  increasing  strength,  making  the 
third  the  maximum  grip.  During  the  third  grip  the  meas- 
ure was  taken  for  the  "forearm  contracted."  (The  metal 
cuff  locates  approximately  the  zone  of  maximum  swell  of  the 
forearm.) 

3.  Circumference  of  Palm. — The  palm  was  fully  opened 
and  the  fingers  held  in  contact.  The  tape  was  snugly  drawn 
around  the  palm  just  below  (on  thumb  side)  the  points 
where  the  palm-creases  disappear  on  the  edges  of  the  palm. 

4.  Circumference  of  Wrist. — The  wrist  circumference 
was  taken  over  the  extreme  bony  knobs,  with  arm  muscles 
relaxed. 

5.  Length  of  Humerus. — In  taking  the  length  of  the 
humerus  the  subject  was  instructed  to  place  his  hand  on 
his  hip ;  then  the  elbow  was  forced  around  to  the  back  as  far 


MEASURING   THE  MUSCLE   SWELL,   OF   THE 
^RM  FOREARM 

MEASURING   THE  CIRCUMFERENCE   OF  THE 
WRIST  PALM 


10  A  STUDY  OF  HANDEDNESS 

as  possible  in  order  to  throw  the  shoulder  end  of  the  humer- 
us out  in  position  to  favor  the  measuring.  (The  less  cloth- 
ing on  the  shoulder  and  arm  the  better,  and  no  heavy  cloth- 
ing was  allowed  to  cover  the  shoulder  during  the  measur- 
ing.) The  brachiometer  was  then  placed  with  its  base  press- 
ing firmly  against  the  elbow  and  the  upright  scale  extending 
along  the  outside  of  the  arm  to  the  shoulder.  The  indicator 
was  pressed  snugly  against  the  head  of  the  humerus"  as 
shown  by  its  bulge  in  front  of  the  shoulder  during  the  back- 
ward movement  of  the  elbow,  and  the  brachiometer  reading 
was  taken  for  the  "length  of  the  humerus." 

6.  Circumference  of  Ann. — In  taking  the  circumfer- 
ences of  the  arm  the  subject  was  first  instructed  to  fold  the 
arm  upon  itself  firmly  by  bending  it  at  the  elbow,  so  as  to 
reveal  the  zone  of  maximum  swell  of  the  biceps.  This  zone 
was  pencil  marked  at  its  center,  and  the  distance  of  the  mark 
from  the  elbow  was  carefully  measured  by  the  brachiometer. 
Another  pencil  mark  was  made  on  the  opposite  side  of  the 
same  arm  and  at  the  same  distance  from  the  elbow  as  shown 
by  the  brachiometer.  Similar  points  were  marked  on  the 
other  arm,  using  the  same  distance  from  the  elbow  for  the 
two  arms.  (The  point  of  maximum  swell  of  the  biceps  is 
midway  of  the  humerus;  and  since  the  point  of  maximum 
swell  is  not  a  mere  point  but  a  zone  from  14  to  %  of  an  inch 
in  width  in  different  arms,  no  allowance  need  ordinarily  be 
made  for  the  difference  in  lengths  of  the  two  arms  of  the 
subject.)  The  brachiometer  was  then  laid  aside  and  the  sub- 
ject instructed  to  extend  the  arm  outward  in  a  straight  line. 
The  tape  was  snugly  adjusted  about  the  ami  as  indicated  by 
the  pencil  marks,  and  the  reading  was  taken  for  the  "arm 
relaxed."  Without  change  in  the  position  of  the  tape,  the 
subject  was  instructed  to  fold  the  arm  firmly  upon  itself 
again  and  then  shake  the  clenched  fist  in  a  brief  but  violent 
quiver.  The  back  and  forth  range  of  the  quiver  was  limited 
to  about  a  fourth  of  an  inch,  and  a  little  warming  up  prac- 
tice was  always  given.  Three  brief  efforts  of  increasing 
strength  were  made  in  each  case,  and  during  the  third  and 
maximum  effort  the  measure  was  taken  for  the  "arm  con- 
tracted." 


MEASURING  THE  HUMERUS 


DATA. 

In  the  following  tabula  are  given  the  measures  of  ap- 
proximately 300  pairs  of  arms,  selected  from  the  total  20,000 
as  follows :  The  first  list  of  200  serial  measures  is  a  random 
selection,  giving  a  working  idea  of  the  general  run  of  arm 
measures  in  living  beings.  The  next  list  is  a  random  selec- 
tion of  40  serial  measures  from  the  group  of  living  left  hand- 
ers,  showing  the  general  run  of  measures  of  left  handed  in- 
dividuals. The  third  list  is  a  random  selection  of  60  serial 
measures  from  the  group  of  Jiving  transfers,  showing  the 
general  run  of  measures  of  individuals  who  have  been  trans- 
ferred by  one  or  more  of  various  causes  stated  or  suggested 
in  so  far  as  known.  The  fourth  list  gives  the  arm  measures 
of  a  half  dozen  cadavers  and  of  a  dozen  *unpieced  human 
skeletons.  The  cadaver  measures  show  the  differences  in 
the  bone  equipment  of  the  two  arms  as  those  differences  ap- 
pear when  the  bones  are  freshly  removed  from  the  human 
body.  The  skeleton  measures  show  the  differences  as  i"e- 
vealed  by  the  bones  when  removed  and  thoroughly  dried. 
(The  skeletons  used  are  a  collection  of  Arikara  Indian  skele- 
tons unearthed  and  prepared  by  Curator  W.  H.  Over,  of  the 
Department  of  Geology  of  the  University  of  South  Dakota. 
They  are  now  on  exhibition  in  the  University  Museum.) 

The  data  are  tabulated  in  fifteen  columns.  In  the  first 
column  is  given  the  number  of  the  individual  as  listed;  in 
the  second  is  given  the  sex,  "M"  indicating  male  and  "F" 
female;  and  in  the  third  column  is  given  the  approximate 
age.  Exact  ages  are  not  needed  in  this  study,  hence  the  age 
is  usually  specified  in  years  (in  months  for  a  few  young  chil- 
dren) ,  referring  to  the  nearest  birthday.  Age  10  thus  means 
that  the  individual  is  over  9>4  and  under  10^  years.  In 
the  fourth  column  is  indicated  the  hand  (and  arm)  whose 
measures  are  given,  "R"  meaning  the  right  hand  and  "L" 
the  left.  In  the  fifth  column  is  given  the  length  of  the  ulna- 
plus  ;  in  the  sixth,  the  circumference  of  the  palm ;  in  the  sev- 
enth, the  circumference  of  the  wrist;  in  the  eighth,     the 


*  A  skeleton  is  known  as  unpieced  if  all  the  bones  are  taken  from  the 
same  body.     Commercial  skeletons  are  often  pieced. 


A  STUDY  OF  HANDEDNESS  13 

length  of  the  humerus;  in  the  ninth,  the  circumference  of 
the  forearm  relaxed ;  and  in  the  tenth,  the  circumference  of 
the  forearm  contracted.  In  the  eleventh  column  is  given 
the  percentage  of  the  forearm  muscle-swell  (computed  by 
dividing  the  difference  of  the  relaxed  and  the  contracted 
muscle  measures  by  the  relaxed  measure).  In  the  twelfth 
and  thirteenth  columns  are  given  the  circumferences  of  the 
arm  relaxed  and  contracted,  respectively;  and  in  the  four- 
teenth column  is  given  the  percentage  of  arm  muscle-swell 
(found  by  dividing  the  difference  of  the  relaxed  and  the 
contracted  muscle  measures  by  the  relaxed  measure) .  In  the 
last  column  are  given  explanatory  notes. 

[The  measures  are  recorded  in  inches,  with  all  fractions 
of  the  inch  expressed  in  sixteenths.  Since  the  denominator 
of  every  fraction  may  be  understood  to  be  sixteen,  no  denom- 
inator is  written  but  it  is  indicated  by  the  colon.  Any  fig- 
ure following  the  colon  indicates  so  many  sixteenths  of  an 
inch.  Thus  14:8  means  14  8-16  inches,  and  6:14  means 
6  14-16  inches.  This  system  of  recording  has  been  adopted 
for  convenience  in  tabulating.  In  reading  the  records  it  will 
be  of  further  material  assistance  for  the  reader  to  remem- 
ber that  the  record  for  the  right  hand  is  always  given  in  the 
first  of  the  two  lines  of  measures  across  the  page,  and  the 
record  for  the  left  hand  is  given  in  the  second.] 


14 


A  STUDY  OF  HANDEDNESS 


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A  STUDY  OF  HANDEDNESS 


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A  STUDY  OF  HANDEDNESS 


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28 


A  STUDY  OF  HANDEDNESS 


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A  STUDY  OF  HANDEDNESS 


39 


MEASTTBES   OF   ABM   BONES    OF    CADAVBBS   AND   OF   UNFIBCBD 

HUMAN  SKBIiETONS. 

The  number  to  the  right  of  the  colon  in  each  case  is  the  numerator 
of  a  fraction  whose  denominator  is  16.  Circumferences  of  bones  were 
taken  midway  of  the  shaft. 

Cadavers. 


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•  Left  handed, 
t  Right  humerus 


had  been  fractured. 


40 


A  STUDY  OF  HANDEDNESS 


TABIiE  SHOWING  ABM  MEASURES  FROM  BIRTH  TO  DECREPIT  AGE 

Each  of  the  three  types  of  handedness  is  given  for  each  20  years.       .Vll   males. 


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9:2   I   9:6 

8: 


9:12 

111  9:8 


9: 
9: 

10: 


9: 
9:3 

8:15 


2   I  8:5 

I  8:2 

lo|  8:13 

13|  9:1 

I 

14!  9:2 

121  8:15 


4.9 
3.8 

3.7 
4.8 

4.8 
4.2 

5.6 
4. 

4.8 
5.8 

4. 
3.4 

3.2 

2.6 

3.3 
4.5 

3.1 

2.5 

2.1 
1.4 

2.1 
2.7 

2.1 
2.7 

2.1 
1.6 

2.2 

2.8 

2.8 
2.1 


4:1 
4: 

3:12 
3:13 

11:1 
10:13 

11: 
11:5 

10:15 
10:13 

12: 
11:11 

11:4 
11:9 

11:9 
11:7 

10:3 
10: 

10: 
10:3 

10:12 
10:10 

9:1 
8:15 

9:4 
9:6 


12: 
11: 

12: 
12: 

12: 
11: 

13: 
12 

12 
12 

12: 

12: 

10: 
10: 

10: 
11 

11: 
11: 

9: 

9: 

9: 
10: 


11.3 

13|   9.3 


:9 

6 
15 

9 
5 


9.7 
11.6 

10.2 
9.8 

8.3 
7.5 

10. 
11.9 

7.9 
7.7 


15    7.5 


9:      I   9 
9:1    I   9 

I 
8:      I   8 
7:131   8 


11 


9: 
9:2 


I   9:2   I   9 
I   9:1    I   9 


:9 
:13 

:11 


6.3 

9.4 
11. 

9.8 


6.9  I 

5.6  I 

6.1  I 

7.3  I 

I 

5.6  I 

6.9  I 

I 

5.8  i 

5.6  I 

6.3  I 

7.5  I 

6.2 


f  Stillborn. 

*  Ri^ht  hander. 

t  Left  hander. 

t  Left  to  right  transfer. 

§  Right  to  left  transfer. 


A  STUDY  OF  HANDEDNESS 


41 


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42  A  STUDY  OF  HANDEDNESS 

Interpretation  of  Data. 

An  examination  of  the  tabulated  data  reveals  the  fact 
that  each  of  the  300  living  subjects  has  longer  bones  in  one 
arm  than  in  the  other.  The  cadavers,  which  readily  lend 
themselves  to  the  most  rigid  treatment,  reveal  the  same 
thing.  The  arm  bones  of  the  human  skeleton,  measured  for 
length,  circumference,  and  weight,  show  that  the  bones  of 
one  arm  are  not  only  longer,  but  proportionately  larger 
around  a^d  heavier,  the  sturdier  bones  being  in  the  right 
arms  of  right  banders,  and  in  the  left  aiTns  of  left  banders. 
Finally,  the  condensed  table  for  ages  shows  that  this  differ- 
ence in  bone  equipment  of  the  arms  is  just  as  evident  at 
birth  as  in  adult  life,  and  just  as  marked  in  youth  as  in 
decrepit  age.  We  are  not  only  right  or  left  handed,  but 
we  are  born  right  or  left  handed,  and  the  arms  themselves 
bear  the  evidence.  This,  then,  is  the  primal  fact  revealed 
by  the  study;  namely,  the  human  being  is  bom  with  a  major 
and  a  minor  arm;  and  we  have  the  following 


MEASURES  FOR  DETERMINING  BORN  HANDEDNESS: 
(The  major  arm  excels  the  minor  arm  in  these  measures.) 

1.  The  length  of  the  ulna-plus. 

2.  The  palm  circumference. 

3.  The  wrist  circumference. 

4.  The  length  of  the  humerus. 

A  nttle  study  of  the  data  will  show  that  these  measures, 
not  unlike  any  measures  known  to  science,  must  be  applied 
with  circumspection.  Bone  injury  and  bone  diseases  are  not 
uncommon,  and  either  injury  or  disease  may  enlarge  or 
shorten  or  stunt  the  growth  of  a  bone.  Any  one  who  at- 
tempts to  diagnose  handedness,  therefore,  must  be  on  the 
lookout  for  the  signs  and  the  history  of  arm  and  shoulder  de- 
formities. Thus  ih  record  76,  on  page  19  we  find  the  right 
humerus  shorter  than  the  left,  though  the  measures  for  the 
ulna-plus,  the  palm,  and  the  wrist,  all  favor  the  right  side. 
With  three  witnesses  against  one  it  is  reasonable  to  suspect 
injury.    The  history  of  the  case  showed  that  the  subject  had 


A  STUDY  OF  HANDEDNESS  43 

suffered  a  broken  right  humerus  ten  years  before,  and  the 
surgeon  who  had  "set  the  bone"  attributed  the  shortening 
of  the  humerus  to  an  "overriding  fracture."  Number  12,  on 
page  35  shows  the  same  thing  with  the  left  arm.  Number 
9  on  page  34  shows  a  short  right  ulna-phis,  with  the 
palm  measures  equal,  the  wrist  measures  favoring  neither 
side,  and  the  larger  humerus  on  the  right.  This  case  could 
readily  be  misinterpreted  by  a  hasty  or  careless  diagnosti- 
cian. An  examination  of  the  arms  revealed  enlargements  of 
both  bones  of  the  right  foreaiTn  with  no  evidence  of  injury 
to  the  left  arm.  This  suggested  a  shortening  of  the  right 
forearm  from  bone  injury.  Further  evidence  was  found  in 
the  fact  that  the  right  forearm  muscle  was  both  small  and 
weak  as  compared  with  the  left,  suggesting  disuse  of  the 
right  forearm.  Finally  the  history  of  the  case  revealed  a 
compound  fracture  of  the  bones  of  the  right  forearm  six 
years  before ;  and  so  the  chain  of  evidence  showing  the  child 
a  bom  right  hander  was  complete.  Such  cases  are  often  met, 
as  may  be  seen  by  the  notes  accompanying  the  tabulated 
measures,  and  the  diagnostician  must  be  ready  in  their  in- 
terpretation. 

The  first  question  which  this  investigation  set  out  to  an- 
swer, namely:  "How  can  we  determine,  de  novo,  whether  a 
child  is  bom  right  or  left  handed  ?"  has  found  its  answer  in 
the  bone  measures  of  the  amis ;  and  we  may  now  turn  to  the 
second  question;  namely,  "How  can  we  distinguish  bom 
handedness  from  acquired  handedness  ?' 

In  record  number  64,  on  page  19,  we  find  that  the  bone 
measures  favor  the  left  side;  that  is,  the  subject  is  a  born 
left  hander;  but  we  find  the  muscle  swells  favoring  the 
right  arm.  Now  muscle  grows  with  use,  and  the  larger 
percentage  of  muscle  swell  reveals  the  arm  that  is  most  in 
use;  that  is,  the  larger  percentage  of  muscle  swell  reveals 
the  adopted  arm.  This  subject  is  a  bom  left  hander,  but 
in  some  way  he  has  acquired  a  dominant  use  of  his  right 
hand.  In  the  note  column  we  find  the  history  that  explains 
the  case ;  namely,  the  parents,  following  tradition,  have  suc- 
ceeded in  transferring  the  child  to  the  right  hand. 


\ 


44  A  STUDY  OF  HANDEDNESS 

Record  number  76,  on  page  19,  reveals  a  transfer  from 
right  to  left.  The  bone  measures,  excepting  the  measure  of 
the  right  humerus  as  we  have  already  noted  for  this  individ- 
ual, reveal  born  right  handedness,  while  the  muscle  swells 
show  that  she  is  using  the  left  arm  the  more  freely.  The 
accompanying  note  in  the  explanatory  note  column  gives  the 
history  that  reveals  the  cause  of  the  transfer. 

The  use  of  a  hand  and  arm  is  thus  revealed  by  the  mus- 
cle swells,  and  the  adopted  aiTn  sooner  or  later  comes  to  have 
the  higher  percentage  of  muscle  swell.  Our  answer  to  the 
second  question;  namely,  "How  can  we  distinguish  born 
handedness  from  acquired  handedness?"  is  therefore  at 
hand.     . 

BORN  HANDEDNESS  IS  REVEALED  BY  THE 
MEASURES  OF  THE  BONES  OF  THE  ARM,  THE  MAJOR 
ARM  HAVING  THE  LARGER  BONES;  ADOPTED 
HANDEDNESS  IS  SHOWN  BY  THE  MUSCLE  SWELL, 
THE  ADOPTED,  OR  PREFERRED,  ARM  HAVING  THE 
HIGHER  PERCENTAGE  OF  MUSCLE  SWELL. 

A  little  study  of  the  data  again  will  show  that  the  mus- 
cle swell  too,  must  be  judged  with  circumspection  if  the 
problem  of  born  and  acquired  handedness  is  to  be  safely  set- 
tled. Record  number  6,  on  page  34,  shows  an  individual  bom 
left  handed,  since  three  witnesses  favor  the  left,  though  one, 
the  ulna-plus,  is  neutral;  but  the  forearm  muscle  swell  fa- 
vors the  right  side,  and  the  arm  muscle  swell  is  neutral.  An 
examination  of  the  arms  revealed  an  enlargement  of  the  left 
ulna  just  above  the  wrist,  affecting  also  the  wrist  measure; 
and  the  left  hand  showed  an  outward  deflection  from  the 
line  of  the  arm.  We  hardly  need  the  history  of  the  case  to 
make  it  clear  that  this  subject  has  just  passed  over  the  line 
of  transfer,  due  to  a  broken  left  ulna  of  short  time  standing, 
so  short  time  indeed  that  the  forearm  muscles  of  the  right 
arm  are  but  little  stronger  than  those  of  the  left,  and  the 
two  arm  muscles  are  just  on  the  neutral  line.  The  history 
given  in  the  explanatory  note,  however,  corroborates  the 
evidence. 


A  STUDY  OF  HANDEDNESS  45 

Record  36,  on  page  36,  shows  a  right-to-left  transfer. 
The  parents  were  not  aware  that  the  child  had  ever  been 
transferred,  and  the  cause  of  the  transference  is  not  defi- 
nitely known.  The  history  of  the  case  revealed  that  the 
child  had  fallen  down  a  flight  of  porch  steps  at  three  years 
of  age  and  injured  the  right  shoulder.  The  attending  physi- 
cian had  the  right  arm  carried  in  a  sling  for  a  few  weeks,  and 
soon  afterwards  the  child  was  "found  to  be  left  handed." 
There  is  little  doubt  that  the  child  adopted  the  left  hand 
while  the  right  ann  was  in  the  sling;  and  then  with  no  at- 
tention given  to  the  normal  handedness  when  the  arm  was 
removed  from  the  sling,  the  child  continued  to  use  the  left 
hand  and  arm. 

Turning  now  to  the  explanatory  note  column  of  the  tab- 
ula, the  reader  may  note  that  a  record  is  there  given  of  each 
case  of  stammering.  (The  term  "stammering"  is  here  used 
to  include  both  stammering  and  stuttering,  since  the  two 
terms  are  absolutely  synonymous  in  ordinary  use.  Stammer- 
ing, technically  speaking,  is  imperfect  enunciation  due  to 
lack  of  control  over  the  muscles  of  articulation,  the  sounds 
being  properly  vocalized;  while  stuttering  is  defective  vo- 
calization, or  defective  voicing  of  sounds.  A  stammerer  is 
likely  to  have  trouble  in  enunciating  initial  syllables  begin- 
ning with  b,  p,  d,  or  t,  but  the  stutterer  repeats  the  sylla- 
bles.) Since  the  prevalence  of  stammering  is  a  matter  to 
be  determined  by  mass  data,  it  may  best  be  handled  with  the 
table  of  summaries. 

The  table  showing  the  summaries  of  measures  of  the 
20,000  pairs  of  arms  is  given  on  page  41.  In  the  first  column 
of  the  table  is  indicated  the  number  of  individuals  whose 
measures  are  included  in  the  summaries.  In  the  second  col- 
umn in  given  the  number  of  those  (included  in  the  first  col- 
umn) who  were  found  to  be  born  right  handed,  and  in  the 
third  column  the  number  found  to  be  born  left  handed,  ac- 
cording to  the  scale  of  measures  already  explained.  In  the 
fourth  and  compound  column  is  recorded  the  number  of 
transfers  classified  in  groups  according  to  the  type  of  hand- 


46  A  STUDY  OF  HANDEDNESS 

edness  shown.  In  the  fifth  column  (also  compound)  is  given 
the  number  of  stammerers,  also  classified  in  groups  accord- 
ing to  handedness.  At  the  foot  of  the  table  is  given  the  pro- 
portionate numbers  of  males  and  females  born  right  handed 
and  left  handed,  the  total  number  of  stammerers  who  began 
to  stammer  under  eight  years  of  age,  and  the  proportion  of 
males  and  females  among  the  stammerers. 

The  summaries  of  the  first  three- columns  show  that  out 
of  20,000  persons  whose  anns  were  measured,  19,207  are 
born  right  handers,  and  793  are  born  left  handers ;  that  is, 

96%  OF  THE  HUMAN  RACE  ARE  RIGHT  HANDED 
BORN,  AND  *47f  ARE  LEFT  HANDED  BORN. 

The  summaries  further  show  that  out  of  19,207  born 
right  handers,  9,502  are  males  and  9,705  are  females,  while 
out  of  793  born  left  handers  498  are  males  and  295  are  fe- 
males; that  is,  born  left  handedness  is  far  more  common 
among  males,  the  ratio  being  about  5  males  to  3  females. 
[Ballard  estimates  about  2  to  1  in  favor  of  males,  but  in  his 
study  he  made  no  distinction  between  born  handedness  and 
acquired  handedness.] 

The  transfer  column  shows  that  out  of  20,000  persons, 
815  (4%)  are  transferred.  Six  hundred  one  of  these  (74% 
of  all  transfers)  are  transferred  by  purposive  interference, 
and  214  (26%  of  all  transfers)  are  transferred  by  accident. 
We  find  no  case  of  puiposive  transference  from  the  right  to 
the  left  hand  [Tradition  favors  the  right  hand,  aaid  left  in 
tradition  means  unlucky],  but  out  of  793  born  left  handers 
we  find  that  601  (76%  of  all  bom  left  handers)  are  trans- 
ferred to  the  right  hand  by  purposive  interference. 

We  also  find  that  out  of  19,207  born  right  handers,  203 
(about  1%)  are  transferred  to  the  left  hand  by  accident,  and 
out  of  793  bom  left  handers,  11  (about  1%)  are  transferred 
to  the  right  by  accident.     Restating  the  facts  of  transfer, 


*  The  literature  on  handedness  is  full  of  estimates  of  the  proportion 
of  right  and  left  handers,  running  from  3%  to  69c;  but  since  none  of  the 
authors  distinguish  between  born  handedness  and  acquired  handedness 
there  is  little  value  in  making  specific  comparisons. 


A  STUDY  OF  HANDEDNESS  47 

we  have  the  following  *approximate  percentages : 

4%  OF  THE  RACE  ARE  TRANSFERRED  TO  THE 
MINOR  ARM.     (1  out  of  about  25  persons.) 

17r  OF  ALL  BORN  RIGHT  HANDERS  ARE  TRANS- 
FERRED TO  THE  LEFT  HAND  BY  ACCIDENT. 

1%  OF  ALL  BORN  LEFT  HANDERS  ARE  TRANS- 
FERRED TO  THE  RIGHT  HAND  BY  ACCIDENT. 

76 '^r  OF  ALL  BORN  LEFT  HANDERS  ARE  TRANS- 
FERRED TO  THE  RIGHT  HAND  BY  PURPOSIVE  INTER- 
FERENCE. 

77%  (over  three-fourths)  OF  ALL  BORN  LEFT 
HANDERS  ARE  TRANSFERRED  TO  THE  RIGHT  HAND. 

The  stammerer  column  shows  that  out  of  20,000  per- 
sons, 390,  or  nearly  2%,  are  stammerers  or  are  -^reported  to 
have  been  stammerers  earlier  in  Hfe  [Ballard  estimates 
not  over  2%  among  normal  children,  and  17%  among  left 
handers  who  write  with  the  right  hand] ;  and  that  340,  or 
87%,  of  these  are  males,  and  51,  or  13%,  are  females.  (Medi- 
cal writers  commonly  refer  to  the  high  percentage  of  male 
stammerers;  and  the  Wisconsin  State  Department  of  Educa- 
tion reports  over  85%.— Educational  News  Bulletin,  Wiscon- 
sin State  Department  of  Education,  Madison,  February  1, 
1917,  p.  2.) 

Out  of  19,004  bom  right  handers  who  have  adopted  the 
right  hand,  120  (about  V^  of  1% )  are  stammerers;  while  out 
of  181  born  left  handers  who  have  adopted  the  left  hand, 
18  (about  l%f)  are  stammerers.  Out  of  203  right-to-left 
transfers,  33  (16% )  are  stammerers,  while  out  of  612  left-to- 
right  transfers,  219  (36% )  are  stammerers.  (Ballard  found 
17%  among  his  "dextro-sinistrals." — Jour,  of  Exp.  Ped.,  Vol. 
1,  No.  4,  p.  309.)  Finally  we  note  that  out  of  the  390  stam- 
merers, 203  (52%)  are  transfers;  and  that  339  of  the  390, 
or  87%  (and  168,  or  83%,  of  the  203  transfers)  are  reported 
to  have  begun  to  stammer  under  8  years  of  age.   [It  is  safe 

*  The  standard  deviation  of  7.8%  makes  rough  estimates  in  place  here. 

**  The  reports  of  earlier  stammering  are  believed  to  be  quite  reliable, 
since  it  is  characteristic  of  the  recovered  stammerer  that  he  well  remem- 
bers his  former  condition  The  readiness  to  conceal  the  defect  is  not  hard 
to  offset  if  the  subject  is  sympathetically  approached.  There  were  79 
cases  of  earlier  stammering  in  the  total  number  of  390  cases,  and  these 
were  carefully  questioned  for  symptoms  before  accepted  as  recovered 
stammerers. 


48  A  STUDY  OF  HANDEDNESS 

to  assume  that  the  number  of  reported  cases  is  somewhat 
low,  since  no  case  was  included  in  the  list  if  the  starting 
time  was  apparently  doubtful.  The  Wisconsin  State  Board 
of  Education  reports  70%  of  stammering  beginning  at  6 
years  or  under.  See  Educational  News  Bulletin,  Madison, 
Feb.  1,  1917,  p.  2.] 


A  STUDY  OF  HANDEDNESS 


49 


( 

3ne-half  of  all  stammerers  are  transfers. 

One-third  of  all  left-to-right  transfers  are  stammerers. 


One-sixth  of  all  right-to-left  transfers 

are  stammerers. 

J 

Less  than  1%  per 
stammerers.             ^ 

cent;  of  pure  handed  individuals 

are 

1 

J 

RELATION  OF  HANDEDNESS  AND  STAMMERING. 


50  A  STUDY  OF  HANDEDNESS 

Restating  the  *facts  of  stammering,  we  have  the  follow- 
ing: 

One-third  of  left-to-right  transfers  are  stammerers. 

One-sixth  of  right-to-left  transfers  are  stammerers. 

About  1  %  of  pure  left  handers  are  stammerers. 

Less  than  ISf  of  pure  right  handers  are  stammerers. 

One-half  of  all  stammerers  are  transfers,  and  four-fifths 
of  all  stammering  begins  before  the  eighth  birthday. 

About  seven-eighths  of  all  stammerers  are  males. 

Several  questions  at  once  arise;  namely,  (1)  How  is  the 
high  percentage  of  stammerers  among  transfers,  especially 
the  left-to-right  transfers,  to  be  accounted  for?  (2)  Why  is 
the  proportion  of  male  stammerers  so  high,  even  though  we 
allow  for  the  fact  that  the  ratio  of  born  left  handed  males  to 
born  left  handed  females  is  about  five  to  three?  and  (3) 
Why  does  stammering  commonly  begin  during  the  early 
years  ?  Any  senous  attempt  to  answer  these  questions  to- 
day must  resort  to  one  or  both  of  two  methods ;' namely,  (1) 
speculation  in  the  field  of  brain  psychologic  and  (2)  experi- 
mental treatment  to  derive  concrete  evidence.  We  may  well 
combine  the  two  methods. 

SPECULATIVE  TREATMENT 
of  the 
CAUSAL    RELATION    BETWEEN    HAND    TRANSFER- 
ENCE AND  STAMMERING. 

The  fundamental  fact  of  handedness,  in  so  far  as  we 
■  can  yet  unravel  it,  is  the  fact  of  congenital  cerebral  asym- 
metry. The  present  day  knowledge  of  brain  psychology  is 
very  incomplete,  but  a  speculative  treatment  of  our  problem 
in  terms  of  the  best  theory  that  physiological  psychology 
has  to  offer  will  be  at  least  better  than  no  attempt  at  ex- 
planation at  all.  It  will  at  least  try  the  theory ;  and  theories 
are  established  or  broken  down  through  use. 

We  may  take  as  our  starting  point,  the  prevaiHng  physi- 


*  Since  the  standard  deviation  on  the  average  number  of  stammerers 
per  thousand  individuals  is  12.7%,  the  proportions  are  given  as  rough 
fractions  rather  than  as  definite  percentages. 


A  STUDY  OF  HANDEDNESS  51 

ological  theory  (1)  that  there  are  *four  highly  specialized 
cortical  centers  involved  in  the  speech  of  the  nomial  adult; 
namely,  two  sensory — the  auditory  and  the  visual,  and  two 
motor — the  vocal  and  the  writing-  (graphic  word)  centers; 
(2)  that  all  four  of  these  centers  are  normally  located  in  one 
(hence  called  superior)  hemisphere  of  the  brain ;  namely,  the 
left  hemisphere  in  the  **born  right  handed  individual,  and 
the  right  hemisphere  in  the  **bom  left  handed  individual; 
and  (3)  that  though  the  muscles  of  the  vocal  organs  are 
anatomically  connected  with  each  hemisphere,  they  are  func- 
tionally connected]jSnly  one ;  and  in  so  far  as  the  hand  is  an 
organ  of  speech,  at  least,  it  shares  the  same  asymmetry. 

Since  the  child  hears  words  freely  before  he  speaks  or 
sees  or  writes  them ;  since  he  speaks  them  freely  before  he 
see»  them,  and  sees  them  freely  before  he  writes  them  free- 
ly, we  may  reasonably  assume  that  the  graphic  word,  or 
writing,  center  is  the  last  to  be  called  into  function.  We 
may  also  assume  that  the  writing  center  is  called  into  func- 
tion whenever  the  child  begins  to  write  or  scribble,  and  this 
is  quite  certain  to  be  before  he  is  8  years  of  age.  Suppose  a 
born  left  handed  child  is  learning  to  write.  If  he  Is  allowed 
to  write  with  the  left  hand,  then  we  may  assume  that  the 
writing  center  is  developed  in  the  right  hemisphere — the 
hemisphere  in  which  the  auditory,  the  vocal,  and  the  visual 
centers  are  already  located.  This  unified  placem.ent  of  word 
centers  we  may  consider  normal  according  to  our  physiologi- 
cal theory.  But  suppose  the  born  left  handed  child  is  re- 
quired to  write  with  his  right  hand.  Then  we  may  assume 
that  the  writing  center  is  developed  in  the  left  (the  inferior) 
hemisphere.  What  will  happen?  We  may  speculate  that 
any  one  of  three  things  will  occur;  namely,  (1)  the  lack  of 
unity  resulting  from  the  location  of  three  of  the  word  cen- 
ters in  one  hemisphere  and  one  in  the  other,  will  bring  func- 
tional disharmony  due  to  the  fact  that  the  neural  currents 


*  If  we  take  the  position  with  Collier  and  others  (see  "Brain,"  Part 
CXXIV,  Vol.  XXXI,  1908,  p.  540)  that  the  existence  of  separate  auditory 
and  visual  speech  centers  rests  upon  the  "slenderest  facts,"  it  will  change 
our  speculation  in  no  significant  respect;  and  few  will  go  so  far  today 
as  to  agree  with  Marie  that  there  is  only  one  speech  center  (see  Sem.  Med., 
23   mai,   1906,   p.   241.) 

**  The  addition  of  this  word  is  suggested  by  this  study. 


52  A  STUDY  OF  HANDEDNESS 

are  ill-timed  or  even  conflicting,  thus  giving  rise  to  speech 
checking,  speech  hesitation,  or  stammering;  (2)  the  free  use 
of  the  right  hand  in  writing  may  firmly  seat  the  writing  cen- 
ter in  the  right  hemisphere  and  this  may  be  followed  by  the 
transference  (the  "dragging  over"  theory)  of  the  three  word 
centers  from  the  left  to  the  right  hemisphere,  thus  giving 
rise  to  extreme  functional  disturbance,  for  a  time  at  least, 
that  may  initiate  stammering  through  lack  of  co-ordination ; 
(3)  since  the  child  may  have  attempted  some  left  hand  writ- 
ing before  formal  writing  work  began,  indeed  may  even  con- 
tinue the  same  when  left  free  to  himself,  two  writing  centers 
or  even  two  sets  of  speech  centers,  one  in  either  hemisphere, 
may   be    developed    (theory    of   ambidexterity    advocates) 
which  in  turn  could  seriously  interfere  with  neural  co-ordina- 
tions and  lead  to  stammering.    In  any  case  we  must  assume 
that  there  is  an  intimate  functional  connection  among  the 
four  word  centers,  such  that  whenever  the  last    developed 
center  (the  writing  center)  is  functioning,  all  the  word  cen- 
ters are  likely  to  function;  and  any  interference  with  this 
functional  unity  may  result  in  turning  the  neural  currents 
into  wrong  or  even  conflicting  channels,  thus  giving  rise  to 
checks,  to  hesitation,  to  stammering.    The  fact  that  no  lesion 
has  so  far  been  discovered,  leaves  us  with  only  the  function 
to  speculate  upon ;  but  any  one  of    the  above    speculations 
gives  us  a  possible  explanation. 

We  may  further  speculate  that  one  child  is  more  readily 
set  to  stammering  than  another  for  the  reason  that  the  inti- 
mate functional  connection  of  the  four  word  centers  is  more 
readily  disturbed  in  one  than  in  another.  The  general  nerv- 
ous stability  is  undoubtedly  a  detemiining  factor.  A  child 
dominantly  vocomotor,  or  linguistic,  may  be  more  difficult  to 
unsettle  than  other  types,  and  we  may  speculate  that  it  is 
for  this  reason  that  stammering  is  less  common  among  fe- 
males. 

When  we  come  to  speculate  with  the  fact  that  stam- 
mering commonly  begins  before  the  age  of  8  years,  we  may 
assume  that  since  this  is  the  period  when  the  language  cen- 
ters are  being  developed,  it  is  also  the  time  when  the  func- 
tional unity  of  these" centers  is  the  least  stable.    The  trans- 


A  STUDY  OF  HANDEDNESS  53 

fers  are  the  likely  stammerers,  probably  for  the  reason  that 
the  unity  of  languag-e  centers  is  so  likely  to  be  disturbed. 
We  may  assume  (1)  that  36%  of  the  left-to-right  transfers 
stammer  for  the  reason  that  this  transference  is  commonly 
accomplished  under  exasperating  conditions,  such  as  nag- 
ging, threatening,  hand  tying,  wearing  of  mittens,  and  so  on 
to  the  limit  of  tradition  and  human  ingenuity,  that  in  them- 
selves superinduce  morbid  sensitivity  and  nervous  instabil- 
ity; .and  (2)  that  16%  of  the  right-to-left  transfers  stam- 
mer because  they  are  transferred  by  injuries  and  treatment 
that  are  themselves  serious  attacks  on  neural  stability, 
though  commonly  of  shorter  duration  than  the  nagging 
era  of  left-to-right  shifting.  We  may  assume  that  the  per- 
centage of  stammering  is  higher  among  pure  left  handers 
than  among  pure  right  handers  for  the  reason  that  so  few 
left  handers  escape  traditional  interference;  and  finally  we 
may  believe  that  there  are  causes  other  than  hand  transfer- 
ence operating  in  the  direction  of  stammering. 


54  A  STUDY  OF  HANDEDNESS 

EXPERIMENTAL  TREATMENT 
of  the 
CAUSAL  RELATION  BETWEEN  HAND  TRANSFER- 
ENCE AND  STAMMERING. 

Having-  concluded  the  speculative  treatment  of  the 
causes  of  stammering,  we  may  now  return  to  experimental 
means  to  discover  whether  or  not  the  main  principle  assumed 
in  the  speculation  is  sound.  We  may  state  our  problem  as 
follows :  Does  writing  with  the  minor  hand  invite  stammer- 
ing? 

In  the  effort  to  get  definite  data  on  this  problem,  two 
subjects  were  chosen  who  were  known  to  be  near  the  stam- 
mering line,  one  just  recovering  from  stammering,  the  other 
just  beginning  to  stammer,  and  subjected  to  composition 
writing  tests.  The  recovering  stammerer  was  required  to 
write  with  the  minor  arm  and  the  stammering  subject  with 
the  major  arm.  The  first  subject  was  a  14-year-old  boy 
whose  arm  measures  are  recorded  under  number  5,  page  30. 
This  boy  was  apparently  in  ordinary  health,  with  a  systolic 
blood  pressure  (auscultatory  method,  sitting  posture)  com- 
monly ranging  from  115  to  120,  a  pulse  pressure  of  32,  usu- 
ally quite  nervous  (esthesiometer  reading  from  19  to  23  on 
back  of  left  hand),  but  with  no  physical  defect  revealed  by 
physical  examination  excepting  a  *  constricted  and  adherent 
prepuce.  He  was  a  born  left  hander  and  his  parents  had 
tried  to  force  the  use  of  the  right  hand,  but  gave  up  when 
the  boy  reached  his  12th  year  still  dominantly  left.  He  had 
stammered  for  several  years,  but  had  shown  no  signs  of 
same  for  a  few  months  previous  to  the  tests.  The  second 
subject  was  the  8-year-old  boy  whose  record  is  number  27, 
on  page  36.  This  child  passed  a  fair  physical  examination. 
His  hearing  range  was  short,  and  he  had  had  adenoids  re- 
moved two  years  before.  His  nerves  were  quite  unstable 
(esthesiometer  reading  15  to  18)  and  he  carried  an  unde- 
scended testicle.  He  was  a  left-to-right  transfer,  due  to 
parental  interference,  and  he  was  beginning  to  stammer. 

The  14-year-old  recovering  stammerer  was  set  to  writ- 
ing compositions  on  various  subjects  of  interest  to  himself, 


*  This  defect  is  significantly  common  in  stammerers. 


A  STUDY  OF  HANDEDNESS  55 

the  writing  being  done  with  the  minor  (right)  hand.  (He 
had  been  required  to  use  this  hand  in  writing  during  the 
years  he  had  stammered.)  He  was  required  to  write  for 
three  twenty-minute  periods  daily,  taking  up  a  new  subject 
as  soon  as  he  lacked  thought  on  the  one  in  hand,  and  he  was 
stopped  at  the  end  of  each  twenty-minute  period  and  asked 
to  tell  what  he  had  written.  If  no  signs  of  stammering  ap- 
peared he  was  excused  from  speaking  and  set  to  writing 
again.  At  the  end  of  the  eighth  twenty-minute  period  (sec- 
ond period  of  the  third  day)  stammering  was  clearly  evi- 
dent and  the  subject  was  excused  from  further  writing.  In 
order  to  try  the  counter  effect,  the  boy  was  set  to  writing 
with  his  left  (minor)  hand,  for  one  twenty-minute  period  a 
day  until  the  results  could  be  determined.  The  stammer 
was  evident  for  a  period  of  eleven  days,  then  disappeared 
v.'ith  occasional  lapses  for  a  period  of  five  weeks.  During 
the  last  four  weeks  the  foiTnal  left  hand  writing  tasks  were 
discontinued  but  the  left  hand  was  used  exclusively  in  what- 
ever writing  was  done.  At  the  end  of  seven  weeks  from  the 
time  of  the  first  experiment,  the  boy  was  given  another  trial 
at  right  hand  writing,  under  the  same  conditions  as  before, 
and  the  stammer  returned  at  the  end  of  the  fifth  twenty- 
minute  period.  Recourse  to  left  hajid  writing  was  again 
taken,  and  the  stammer  continued  for  seventeen  days  with 
eight  weeks  of  occasional  lapses,  then  the  formal  writing  was 
ceased  but  the  left  hand  was  used  exclusively  in  writing  and 
is  in  use  at  the  time  of  the  present  writing,  six  months  hav- 
ing elapsed  since  the  stammer  disappeared. 

The  eight-year-old,  left-to-right  transfer,  who  was  just 
beginning  to  stammer,  was  using  his  right  hand  in  what- 
ever writing  he  had  to  do,  including  a  fifteen-minute  daily 
writing  lesson  in  school.  The  parents  and  the  teacher  con- 
sented to  allow  the  boy  to  use  his  left  (major)  hand  in  his 
writing,  in  order  to  see  what  the  result  would  be  in  terms 
of  stammering.  The  boy  was  then  set  to  writing  formal 
writing  lessons  for  two  fifteen-minute  periods  daily,  one  in 
the  forenoon  and  the  other  in  the  afternoon.  The  writing 
was  done  with  the  left  (major)  hand,  and  the  subject  was 
ready  to  co-operate  by  doing  all  his  writing  with  the  same 
hand.  After  two  weeks,  daily  compositions  on  topics  of 
interest  to  the  bov  were  substituted  for  the  formal  writing, 


56  A  STUDY  OF  HANDEDNESS 

in  order  to  involve  the  speech  centers  fully.  The  composi- 
tions were  written  in  three  ten-minute  periods,  with  five- 
minute  intermissions  for  telling  aloud  what  he  had  written. 
The  boy  was  a  slow  and  laborious  writer  and  usually  whis- 
pered the  words  as  he  wrote  them  (*Conradi  found  that 
stammerers  are  as  a  rule  backward  in  school  work,  but  sug- 
gests that  this  is  probably  due  to  psychic  depression  brought 
about  by  mockery.  We  have  no  evidence  so  far  that  shows 
the  stammerer  below  average  mentally,  though  we  do  find 
him  below  in  school  work  involving  speech). 

His  speech  during  the  five-minute  "telling  intermis- 
sions" was  closely  watched.  Not  until  the  twenty-second  day 
of  composition  writing  could  it  be  unmistakably  seen  that 
the  stammer  was  disappearing.  At  the  end  of  forty-seven 
days  of  composition  writing  the  boy  carried  on  conversation 
without  hesitation,  and  the  composition  writing  was  discon- 
tinued, though  the  writing  in  school  and  elsewhere  was  done 
with  the  left  hand.  After  a  ten-day  respite,  during  which 
time  the  boy  reported  no  serious  lapse  of  speech,  it  was  ar- 
ranged to  try  writing  with  the  right  (minor)  hand.  The 
three  ten-minute  composition  periods,  with  five-minute  "tell- 
ing intermissions"  were  used  as  before,  and  the  school  writ- 
ing was  discontinued  by  two  weeks  of  vacation.  On  the 
third  day  of  the  composition  writing  with  the  right  (minor) 
hand,  evidence  of  stammering  reappeared ;  and  on  the  fifth 
day  the  child  was  unable  to  handle  words  beginning  with  the 
letter  "b."  The  writing  was  then  resumed  with  the  left 
(major)  hand  and  carried  on  as  before  for  twenty-seven  days 
before  the  stammer  was  lost. 

These  two  bits  of  experimental  evidence,  insufficient  in 
themselves  to  settle  questions  that  arise,  but  rather  point- 
ing the  way  for  further  study,  are  unmistakable  evidence 
that  there  is  an  intimate  relation  between  minor  hand  writ- 
ing and  stammering.  They  seem  to  give  depth  of  meaning 
to  the  experimental  evidence  already  produced,  and  they 
strengthen  faith  in  the  fundamental  theories  of  brain  psy- 
chology. We  are  driven  to  the  conclusion  at  least  that  the 
tradition  that  would  force  all  left  handed  children  to  write 
with  the  right  hand  is  a  tradition  as  dangerous  as  it  is  ig- 
norant of  possible  consequences. 


•  Journal  of  Educational  Psy.,  Vol.  Ill,  No.  1,  pp.  35-38. 


PART  II. 

SHOULD   THE   LEFT  HANDED   CHILD   BE   TRAINED 

TO  ADOPT  THE  RIGHT  HAND? 


PROBLEM— SHOULD  THE  LEFT  HANDED  CHILD  BE 
TRAINED  TO  ADOPT  THE  RIGHT  HAND? 

Material  and  Handling. 

The  material  for  this  part  of  the  study  consists  of  the 
measures  of  hand  and  arm  skill  of  1125  individuals  of  whom 
one-third,  or  375,  were  pure  rig-ht  handers  (born  right  and 
adopted  right),  one-third,  or  375,  pure  left  handers  (born 
left  and  adopted  left)  and  one-third,  or  375,  transfers  (part 
right-to-left,  and  part  left-to-right).  Subjects  were  chosen 
to  reveal  the  hand  skill  of  young  children,  of  youth,  and  of 
adults  of  both  sexes.  The  individuals  represent  purely  chance 
selection  within  the  age  limits  specified. 

Three  tests  of  hand  and  arm  skill  were  used ;  namely, 

1.  The  shot  tube  test. 

2.  The  peg  board  test. 

3.  The  tapping  rate  test. 

The  shot  tube  test  was  chosen  for  a  test  chiefly  of  hand 
skill ;  the  tapping  rate  test,  a  test  chiefly  of  arm  ability,  and 
the  peg  board  test,  a  test  of  combined  hand  and  arm  skill  in 
about  equal  proportion.  All  three  of  the  tests  give  scores 
large  enough  to  show  comparative  skill. 

DESCRIPTION  OF  SKILL  TESTS. 

1.    Shot  Tube  Test. 

The  shot  tube  test  is  a  test  to  determine  the  number  of 
seconds  required  for  the  subject  to  pick  up  with  the  fingers 
25  quarter-inch  steel  balls,  one  at  a  time,  and  drop  them  into 
a  vertical  tube  6^  inches  high  and  with  a  mouth  three- 
eights  of  an  inch  in  diameter.  Thirty-five  of  the  steel  balls, 
called  "shot"  for  convenience,  were  placed  in  a  wooden  dish 
made  with  a  hopper  bottom  so  that  the  shot  could  always  be 
readily  located.  The  dish  containing  the  shot  was  placed 
just  to  the  right  of  the  loading  tube  when  the  loading  was 
to  be  done  with  the  right  hand,  and  similarly  to  the  left  of 
the  tube  for  the  left  hand.    Each  subject  was  allowed  three 


THE  SHOT  TUBE  TEST 


60  A  STUDY  OF  HANDEDNESS 

trials  with  each  hand  before  the  test  began,  and  he  was  en- 
couraged to  load  as  fast  as  possible.  When  ready  for  the 
test,  the  subject  was  instructed  to  hold  the  tube  firmly  with 
one  hand,  and  to  place  the  other  hand  (hand  to  be  tested) 
with  the  fingers  at  the  mouth  of  the  tube  as  if  preparing  to 
drop  a  shot.  A  stop  watch  was  held  at  his  ear  with  instruc- 
tions to  begin  picking  and  loading  the  instant  the  stop  watch 
was  clicked  to  start,  and  to  continue  until  the  tube  was  filled 
with  shot  irrespective  of  the  number  dropped.  The  operator 
stopped  the  watch  the  instant  the  25th  ball  clicked  in  its 
place  in  the  tube. 

Two  series  of  record  trials,  four  trials  in  each  series, 
were  made  in  the  following  order:  First  series — first  trial 
with  the  major  hand,  second  and  third  trials  with  the  minor 
hand,  fourth  trial  with  the  major  hand.  After  a  pause 
of  two  minutes,  the  second  series  was  given — first  trial  with 
the  minor  hand,  second  and  third  trials  with  the  major  hand, 
and  the  fourth  with  the  minor  hand.  The  average  of  the 
four  records  made  with  each  hand  was  tabulated  for  the 
final  record. 

2.    The  Peg  Board  Test. 

The  peg  board  test  is  a  test  to  determine  the  number 
of  pegs  the  individual  can  place,  or  load,  in  an  ordinary  kin- 
dergarten peg  board  (Mrs.  Putnam's  Peg  Board)  in  30  sec- 
onds. The  subject  was  seated  at  a  table  with  a  100-hole  peg 
board  in  front  of  him.  The  100  pegs  were  contained  in  the 
pasteboard  box  placed  just  to  the  right  of  the  peg  board 
when  the  loading  was  to  be  done  with  the  right  hand,  and 
in  a  similar  position  on  the  left  when  the  loading  was  to  be 
done  with  the  left  hand.  Each  subject  was  allowed  three 
trials  with  each  hand  before  the  test  began^  He  was  in- 
structed to  load  as  fast  as  possible  and  to  place  the  pegs  in 
order  in  the  25  holes,  beginning  at  the  hole  farthest  from  the 
peg  box.  When  ready  for  the  test  the  subject  was  directed 
to  place  the  index  finger  of  the  loading  hand  over  the  first 
hole  to  be  loaded,  and  to  steady  the  peg  board  with  the  other 
hand.    A  stop  watch  was  held  at  his  ear  with    the    under- 


A  STUDY  OF  HANDEDNESS  61 

standing  that  the  loading  was  to  begin  when  the  watch  was 
clicked  to  start  and  that  the  loading  was  to  continue  until 
the  watch  was  clicked  to  stop.  Two  series  of  record  trials, 
four  trials  in  each  series,  were  made  and  recorded  as  already 
described  in  the  shot  tube  test. 

3.    The  Tapping  Rate  Test. 

The  tapping  rate  test  used  was  the  familiar  test  to  de- 
termine the  number  of  taps  with  a  pencil  that  the  arm  is  able 
to  make  in  a  given  time.  The  subject  was  seated  at  a  table 
across  which  was  drawn  a  long  strip  of  adding  machine  pa- 
per. She  was  handed  a  hard  lead  pencil  about  four  inches 
long  and  instructed  that  the  object  was  to  make  as  many 
taps  (dots)  on  the  paper  as  possible  in  30  seconds,  holding 
the  hand  in  one  position  while  the  operator  moved  the  pa- 
per slowly  along.  (No  machinery  for  moving  or  recording 
was  used.)  The  operator  sat  to  the  left  of  the  subject  and 
moved  the  paper  slowly  from  right  to  left  when  the  tapping 
was  done  with  the  right  hand,  and  to  the  right  of  the  sub- 
ject with  the  movement  of  the  paper  reversed  when  the  tap- 
ping was  done  with  the  left  hand.  When  ready  for  the  test 
the  operator  took  the  stop  watch  in  one  hand  and  seized  the 
end  of  the  paper  strip  with  the  other  hand.  The  subject 
was  instructed  to  begin  tapping  the  instant  the  stop  watch 
was  clicked  at  his  ear  and  to  continue  until  the  paper  was 
jerked  from  under  his  pencil  at  the  end  of  the  30  seconds. 
One  practice  trial  with  each  hand  was  allowed  before  the 
record  trials  began.  Two  record  trials  with  each  hand  were 
made,  the  first  with  the  major  hand,  the  second  and  third 
with  the  minor  hand,  and  the  last  with  the  major  hand.  The 
taps  were  counted  by  marking  them  off  in  fives,  and  the 
average  of  the  two  trials  with  each  hand  was  tabulated  for 
the  final  record. 


62  A  STUDY  OF  HANDEDNESS 

DATA. 

In  the  first  of  the  following  tabula  (page  63)  are  given 
the  measures  of  the  hand  and  arm  skill  of  seventy-five  boys 
from  14  to  16  years  of  age,  as  shown  by  the  shot  tube  test. 
Twenty-five  of  these  boys  were  shown  by  brachiometer 
measures  to  be  pure  right  banders,  that,  is  born  right  hand- 
ed and  using  right;  twenty-five  were  pure  left  banders 
(bom  left  and  using  left),  and  twenty-five  were  transfers. 
The  tabulated  record  for  each  individual  shows  five  facts ; 
namely,  (1)  the  number  of  the  individual  in  the  list ;  (2)  the 
age — given  to  the  nearest  birthday  for  adults,  but  expressed 
in  years  and  months  for  individuals  under  25  years  of  age. 
[Age  16:2  means  16  years  and  2  months] ;  (3)  the  record 
made  by  the  right  hand  in  the  given  test:  (4)  the  record 
made  by  the  left  hand,  and  (5)  the  range  of  skill,  or  the  dif- 
ference between  the  skill  records  of  right  and  left  hands. 
[Since  part  of  the  transfers  are  right-to-left,  and  part  left- 
to-right,  their  records  are  given  in  the  same  columns  under 
the  headings  "Major"  and  "Minor"  instead  of  "R"  (right) 
and  "L"  (left)  hands.] 

In  the  second  tabulum  (page  64)  are  recorded  the  meas- 
ures of  hand  and  arm  skill  of  seventy-five  women  (twenty- 
five  of  each  handedness  group)  from  21  to  24  years  of  age, 
as  shown  by  the  peg  board  test.  The  five  columns  of  data 
are  given  under  headings  the  same  as  for  the  shot  tube 
test  just  explained. 

In  the  third  tabulum  (page  65)  the  measures  of  hand 
and  arm  skill  of  seventy-five  girls  (twenty-five  of  each 
handedness  group)  from  7  to  9  years  of  age,  as  shown  by  the 
tapping  rate  test.  The  five  columns  of  data  are  given  under 
headings  the  same  as  for  the  shot  tube  and  peg  board  tests. 

The  column  average  is  given  at  the  foot  of  each  column 
to  show  the  central  tendency,  and  the  average  deviation 
(A.  D.)  from  the  average  is  given  to  show  the  deviation  from 
the  central  tendency. 


A  STUDY  OF  HANDEDNESS 


63 


SHOT    TUBE    TEST. 

(Records  indicate  number  of  seconds  and  lOths  of  seconds  required  to  load 

25  shot.) 

14  to  15  Year  Old  Boys.  (Over  1314  and  Under  1«J^  Years.) 


Pure  Right  Handers. 

Pu 

re  Left  Hand 

ers. 

Transfers. 

i- 

s 

3 

6 

-1 

0)   ra 

6 
be 

6 
be 

-1 
0  cS 

c 

6 

00 

•■-1  s 

C 

^ 

< 

ax 

jffi 

C 

< 

XX 

Jffi 

« 

< 
16:5 

41.2 

SK 

a 

1       .  . 

16:2 

39.4 

44.2 

4.8| 

16:2 

35.2 

30. 

5.2 

42.6     1.4 

2      .. 

16:5 

30.6 

39. 

8.4| 

15:11 

41.2 

38.4 

2.8 

14:5 

47. 

49.2    2.2 

3      .. 

15:4 

35.6 

42.6 

7.    1 

15:7 

42.6 

39. 

3.6 

13:10 

49.4 

50.4     1. 

4      .. 

16:4 

35.4 

41.2 

5.8 

15:5 

45.4 

40.2 

5.2 

16: 

36.2 

38.2     2. 

5      .  . 

15:4 

34.8 

40. 

5.2 

14:3 

44.8 

42. 

2.8 

13:9 

48.6 

51.2     2.6 

6      .  . 

15:1 

38.4 

44.2 

5.8 

15:9 

40.8 

35.2 

5.6 

16:1 

36.2 

38.4     2.2 

7      .  . 

]5:8 

33.8 

40. 

6.2 

14:3 

45.6 

40.4 

5.2 

15:3 

43.6 

41.6     1. 

8      .  . 

14:8 

44.2 

50.2 

6. 

15:4 

51.2 

45.2 

6. 

15:11 

38.4 

39.4     1. 

9    ... 

14: 

44.4 

51.6 

7.2 

14:3 

43.2 

40.4 

2.8 

15:11 

39.2 

41.6     2.4 

10      .  . 

14:9 

33.4 

40.2 

6.8 

15: 

42.2 

39. 

3.2 

16:4 

33. 

34.21   1.2 

11      .  . 

14:2 

39.4 

44.4 

5. 

16:4 

36!" 

32.8 

3.2 

13:8 

42.6 

44.2 

1.6 

12      .  . 

15:2 

37.2 

45.6 

8.4 

16:3 

40.2 

36.2 

4. 

16:2 

33. 

36.6 

1   3.6 

13      .  . 

13:6 

■47.4 

52.2 

4.8 

13:6 

52.2 

46.4 

5.8 

13:9 

44.2 

45.8 

1.6 

14      .  . 

15:7 

40.6 

44.8 

4.2 

13:9 

50.6 

45.8 

4.8 

13:10 

48.8 

50.4 

1.6 

15      .. 

15:9 

39.6 

46. 

6.4 

13:7 

52. 

47.2 

4.8 

14:4 

43. 

45.4 

2.4 

16      .. 

14:3 

46.2 

50.8 

4.6 

14:5 

46. 

42.6 

3.4 

15:9 

43.2 

44. 

.8 

17      .. 

14:10 

45.2 

49.2 

4. 

16:2 

41.8 

35.8 

6. 

14:5 

47.2 

49.4 

2.2 

18      .  . 

15:1 

38.2 

43.4 

5.2 

14:10 

47.6 

40.2 

7.4 

15:7 

39.2 

39.4 

.2 

19      .  . 

13:9 

43. 

48.8 

5.8 

15:8 

45. 

38.8 

6.2 

13:7 

45.6 

46.4 

.8 

20      .. 

13:11 

46.8 

52.8 

6. 

15:3 

44.2 

40.2 

4. 

15:1 

40.2 

44.8 

4.6 

21      .  . 

14:3 

37.4 

43. 

5.6 

14:7 

45.6 

41. 

4.6 

15:2 

45.2 

45.0 

.4 

22      .  . 

13:8 

39.6 

44.2 

4.6 

13:10 

51.4 

44.2 

7.2 

14:11 

44.8 

45.6 

.8 

23      .  . 

16:1 

32.2 

38.4 

6.2 

15:9 

42.2 

37.8 

4.4 

15:4 

40.8 

43.8 

3. 

24      .  . 

15:4 

38.2 

44.8 

6.6 

14:1 

48.2 

42.6 

5.6 

15:4 

40.4 

41. 

.6 

25      .  . 

14: 

40. 

45.2 

5.2 

14:7 

53.2 

44.8 

8.4 

15:10 

38.6 

40. 

1.4 

1 

373:1| 

981.0 

1126.8 

145.8||374:6 

1128.4 

1006.2 

122.21 

376:8 

1049.6 

1092.2(42.6 

Av.    1 

14:11| 

39.24 

45.072 

5. 8321115: 

45.136 

40.248 

4.8881 

15:1 

41.984  43.68811.70 

•A.   D.| 

3.65 

3.33 

.8811 

3.79 

3.19 

1.211 

3.79 

3.641   .81 

*  Average  Deviation   from   the  average  which   is   shown  just  above  in 
each  case. 


64 


A  STUDY  OF  HANDEDNESS 


PEG  BOARD. 

(Records  indicate  number  of  pegs  placed  in  30  seconds.) 
21  to  24  Year  Old  Women.     (Over  20V^  and  Under  24 1^  Tears.) 


Pure  Right  Handers. 

Pure  Left  Handers. 

Transfers. 

« 

Si 

3 

0) 

be 
< 

-1 

c 

bD 

KX 

-1 

3^ 

c 

6 

fcX) 

tu  CO 

bo 
S 
ai 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

14 

16 

17 

18 

10 

20 

21 

22 

23 

24 

25 

22:4 

21:3 

22:2 

24:1 

23:4 

22:1 

23:2 

20:6 

21:4 

22:8 

20:7 

21: 

22:6 

23: 

22:2 

21:2 

23:3 

24:4 

23:1 

20:8 

21:2 

23:5 

23:4 

24: 

24:4 

38 
34 
40 
42 
36 
36 
32 
36 
34 
34 
32 
32 
37 
41 
34 
32 
30 
38 
36 
34 
32 
37 
36 
42 
41 

34 
30 
36 
34 
30 
28 
28 
28 
27 
30 
28 
30 
34 
35 
30 
26 
25 
34 
28 
31 
27 
29 
31 
36 
37 

4 
4 
4 
8 
6 
8 
4 
8 
7 
4 
4 
2 
3 
6 
4 
6 
5 
4 
8 
3 
5 
8 
5 
6 
4 

22:11 

23:2 

20:11 

24:3 

23:9 

23:4 

22:11 

21:9 

20:9 

21:6 

21:8 

24:4 

23:3 

22:10 

23:9 

22:11 

23:8 

22:10 

21:7 

22:4 

24:1 

23:8 

23:2 

21:9 

20:11 

34 
34 
31 
36 
36 
26 
34 
32 
28 
27 
26 
33 
35 
30 
32 
34 
33 
33 
29 
30 
32 
28 
35 
32 
31 

38 
40 
35 
40 
39 
30 
40 
36 
33 
34 
34 
38 
39 
34 
38 
39 
38 
37 
32 
34 
34 
32 
39 
35 
33 

4 
6 
4 
4 
3 
4 
6 
4 
5 
7 
8 
5 
4 
4 
6 
5 
5 
4 
3 
4 
2 
4 
4 
3 
2 

22:8 

20:6 

20:11 

21:9 

23:8 

23:11 

24:4 

22:10 

22:5 

20:7 

21:11 

24:3 

23:9 

22:5 

23:9 

22:4 

20:10 

21:8 

23:7 

24: 

23:9 

23: 

22:8 

23:5 

21:10 

33 
30 
34 
33 
32 
34 
34 
33 
33 
32 
28 
34 
:J5 
33 
35 
34 
31 
30 
34 
36 
S5 
33 
33 
35 
32 

29 
28 
32 
32 
29 
32 
33 
30 
33 
30 
28 
34 
34 
32 
34 
34 
30 
28 
32 
35 
34 
31 
33 
33 
30 

1 

2 
2 
1 
3 
2 
1 
3 
0 
2 
0 
0 
1 
1 
1 
0 

1 

2 
2 
1 
1 
2 
0 
2 
2 

|560:11|     896 

766|      130  1568:      |      791|      901]      110| 

566:9 

8261      7901      36 

Av   [  22:5    35:84 
*A.    D 2.74 

30:64       5.2  |   22:9 
2.85    1.52| 

31.64 
2.43 

36.041      4.4 
2.60|   1.07 

22:7    33.04 
1.32 

31.60  1.44 
1.84     .86 

*  Average  Deviation   from   the  average  which  is   shown   just  above  in 
each   case. 


A  STUDY  OF  HANDEDNESS 


65 


TAPPING  RATE. 

Time — 30  seconds. 

(The  records  indicate  the  number  of  taps  in  30  seconds.) 
7  to  9  Year  Old  Girls  (Over  61/2  and  Under  91/2  Years.) 


i 

1 

Transfers: 

Pure  ri 

1 
ght  handers. 

Pure  left 

handers. 

1st  ten  right-to-left; 
others  left-to-right.) 

(0 

-4-)  ^ 

'd 

6 

-t-J  ^ 

^'^ 

0 
6x1 

S-d 

^^ 

s 

6 

< 

r; 

Pi  1 

6 

< 

0    CO 

c 

6 
bo 

< 

•1—1  c 

si  d 

.S3 

C 

"1 

7:10 

142 

118 

24 

7: 

3 

121 

140 

19| 

9: 

142 

134 

8 

2 

8: 

145 

126 

19 

7: 

118 

138 

20i 

7: 

7 

135 

127 

8 

3 

6: 

7 

129 

112 

17 

8: 

3 

126 

145 

191 

9: 

1 

126 

120 

6 

4 

7: 

6 

139 

115 

24 

8- 

3 

130 

150 

20 

7: 

9 

136 

129 

7 

5 

8: 

11 

151 

132 

19 

7: 

6 

118 

137 

19 

8: 

3 

142 

132 

10 

6 

8: 

147 

125 

22 

7 

4 

122 

135 

13 

7 

10 

139 

133 

6 

7 

9: 

3 

148 

130 

18 

8: 

8 

128 

143 

15 

6: 

10 

127 

121 

6 

8 

7: 

4 

139 

121 

18 

8: 

10 

132 

149 

17 

7: 

8 

134 

125 

9 

9 

8: 

2 

144 

114 

30 

9. 

1 

123 

148 

25 

6: 

8 

120 

118 

2 

10 

7: 

11 

141 

117 

24 

8: 

6 

121 

145 

24 

8: 

11 

131 

124 

7 

11 

8: 

10 

142 

120 

22 

8: 

120 

141 

21 

8 

5 

137 

129 

8 

12 

9 

5 

151 

140 

21 

7 

7 

117 

136 

19 

6 

8 

124 

122 

2 

13 

8 

4 

148 

121 

27 

7 

9 

118 

139 

21 

7 

3 

132 

128 

4 

14 

6 

9 

124 

110 

14 

9 

4 

129 

146 

17 

8 

2 

133 

122 

11 

15 

7 

2 

140 

124 

16 

7 

10 

120 

141 

21 

8 

10 

141 

133 

8 

16 

7 

8 

141 

128 

13 

8 

1 

128 

144 

16 

9 

4 

121 

115 

6 

17 

9 

4 

150 

130 

20 

7 

9 

121 

139 

17 

8 

9 

142 

135 

7 

18 

i   7 

5 

134 

116 

18 

7 

1 

125 

137 

12 

8 

■6 

133 

127|   6 

19 

6 

11 

134 

111 

23 

6 

:8 

111 

125 

14 

8 

:7 

132 

122 

1   10 

20 

8 

9 

147 

122 

25 

9 

■5 

139 

158 

19 

7 

:9 

130 

124i    6 

21 

8 

5 

148 

120 

28 

6 

:9 

112 

121 

9 

8 

:9 

141 

1321   9 

22 

7 

:10 

144 

116 

28 

8 

:8 

130 

147 

17 

8 

:6 

137 

126 

!  11 

23 

8 

:7 

150 

128 

22 

9 

130 

151 

21 

8 

:11 

142 

132|   10 

24 

9 

149 

124 

25 

8 

•4 

121 

145 

24 

7 

:3 

133 

1211   12 

25 

8 
202 

■9 
•8 

155 

128 

27 

7 

:11 

120 

141 

21 

9 

:3 

147 

1351   12 

1  3592 

I  3048 

1   544 

11200 

:10 

1  3080 

3541 

1   460 

204 

:6 

1  3357 

1  3166 

1  191 

Av 

8:1  1 

43:68 

121.9; 

I     21.7 

6  8:0  ] 

L23.2 

141.64 

18.4 

8:2  13 

4.28  ] 

L26.64 

7.64 

•A. 

D 

.6.04 

5.92 

3.7( 

) 

5.20 

5.70 

2.96 

5.57 

4.77 

2.13 

*  Average  Deviation   from  the  average  which   is   shown   just  above  in 
each  case. 


66  A  STUDY  OF  HANDEDNESS 

The  foregoing  tabulated  measures  were  given  as  sam- 
ples of  the  general  run  of  the  measures  of  hand  and  arm 
skill  as  shown  by  each  of  the  three  tests  employed.  The  fol- 
lowing tabulation  gives  the  summary  of  skill  tests  of  the 
entire  1125  individuals,  grouped  as  follows: 

1.  The  seventy-five  14-16  year  old  boys,  tested  with  the 
shot  tube. 

2.  Three  hundred  men,  40-50  years  of  age  (over  39^4 
and  under  50>^  years),  100  men  in  each  of  the  three  hand- 
edness groups,  tested  with  the  shot  tube. 

3.  The  seventy-five  21-24  year  old  women,  tested  with 
the  peg  board. 

4.  Three  hundred  men,  50  to  60  years  of  age  (over  49^ 
and  under  60^  years),  100  men  in  each  of  the  three  handed- 
ness groups,  tested  with  the  peg  board. 

5.  The  seventy-five  7-9  year  old  girls,  tested  for  the 
tapping  rate. 

6.  Three  hundred  women,  30-40  years  of  age,  (over 
29 >4  and  under  40>^  years),  100  women  in  each  of  the  three 
handedness  groups,  tested  for  the  tapping  rate. 

Beginning  at  the  left  of  the  page  the  first  column  gives 
the  age  range  of  the  specified  group  of  pure  right  handers, 
the  second  column  gives  the  average  age  of  the  group  (14 :11 
means  14  years  and  11  months) ;  the  third  column  gives  the 
average  skill  shown  by  the  right  hand ;  the  fourth,  the  aver- 
age skill  shown  by  the  left  hand ;  and  the  fifth,  the  average 
range  of  skill,  or  the  difference  between  the  average  records 
of  right  and  left  hands.  The  next  four  columns  give  similar 
facts  for  the  pure  left  handers,  and  the  last  four  columns 
similar  facts  for  the  transfers.  The  average  deviation  (A. 
D.)  from  the  average  is  given  just  below  the  average  in  each 
case  to  show  the  deviation  from  the  central  tendency. 


A  STUDY  OF  HANDEDNESS 


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68  A  STUDY  OF  HANDEDNESS 

INTERPRETATION  OF  DATA. 
1.    Shot  Tube  Data. 

The  summary  of  the  shot  tube  tests  with  seventy-five 
14-16  year  old  boys  shows  (1)  that  25  pure  right  handed 
boys,  averaging  14  years  and  11  months  of  age,  require  on 
the  average  39.24  seconds  to  load  25  shot  with  the  right 
hand,  and  45.07  seconds  for  the  left  hand ;  (2)  that  25  pure 
left  handed  boys,  averaging  15  years  of  age,  require  on  the 
average  45.14  seconds  to  load  25  shot  with  the  right  hand, 
and  40.25  seconds  for  the  left  hand ;  and  (3)  that  25  trans- 
ferred boys,  averaging  15  years  and  1  month  of  age,  require 
on  the  average  41.98  seconds  to  load  the  25  shot  with  the 
major  hand,  and  43.69  seconds  for  the  minor  hand.  These 
facts  mean  that  the  pure  left  handed  boy  is  about  as  skillful 
with  his  left  hand  as  the  pure  right  handed  boy  is  with  his 
right  hand,  but  that  the  transferred  boy  falls  below  the  pure 
right  and  the  pure  left  handed  boy  in  major  hand  skill.  The 
skill  ranges  show  that  the  pure  right  handed  boy  has  a 
right  hand  skill  ranging  5.83  seconds  better  than  that  of 
the  left  hand ;  that  the  pure  left  handed  boy  has  a  left  hand 
skill  ranging  4.89  seconds  better  than  that  of  the  right  hand, 
and  that  the  transferred  boy  has  a  major  hand  skill  ranging 
only  1.7  better  than  that  of  the  minor  hand.  The  shot  tube 
tests  with  the  three  hundred  50-60  years  old  men  show  (1) 
that  100  pure  right  handed  men,  averaging  44  years  and  4 
months  of  age,  require  on  the  average  37.36  seconds  to 
load  25  shot  with  the  right  hand,  and  42.07  second  for  the 
left  hand ;  (2)  that  100  pure  left  handed  men,  averaging 
46  years  and  3  months  of  age,  require  on  the  average  41.84 
seconds  to  load  25  shot  with  the  right  hand,  and  37.5  sec- 
onds for  the  left  hand;  (3)  that  100  transferred  men,  aver- 
aging 45  years  and  8  months  of  age,  require  on  the  average 
39.21  second  to  load  25  shot  with  the  major  hand  and  41.53 
seconds  for  the  minor  hand.  These  facts  mean  that  the 
pure  right  handed  man  and  the  pure  left  handed  man  are 
about  equal  in  hand  skill,  but  that  the  transferred  man  falls 
below  the  pure  right  hander  and  the  pure  left  hander  in 
extreme  skill.     The  skill  ranges  show  that  the  pure  right 


A  STUDY  OF  HANDEDNESS  69 

handed  man  has  a  right  hand  skill  ranging  4.73  seconds 
better  than  that  of  the  left  hand ;  that  the  pure  left  handed 
man  has  a  left  hand  skill  ranging  4.34  seconds  better  than 
that  of  the  right  hand,  and  that  the  transferred  man  has  a 
major  hand  skill  ranging  only  2.32  seconds  better  than  that 
of  the  minor  hand.  According  to  the  shot  tube  test,  there- 
fore, it  appears  that  both  the  pure  right  and  the  pure  left 
hander  have  a  major  hand  of  comparatively  high  grade  skill 
and  a  minor  hand  of  comparatively  low  grade  skill,  while 
the  transfer  has  two  hands  of  about  equal  and  ordinary  skill. 

It  may  be  noted  in  passing  that  the  pure  left  hander  in 
each  group  falls  below  the  pure  right  hander  in  skill  range, 
veering  toward  the  transfer  type  of  skill.  This  may  be  ex- 
plained by  the  fact  that  nearly  all  born  left  banders  meet 
more  or  less  puiTDOsive  interference  tending  to  transfer  them 
to  the  right  hand  in  accordance  with  tradition.  The  pure 
left  banders  of  this  study  are  pure  only  in  the  sense  that 
they  are  still  using  the  hand  which  they  were  born  to  use ; 
but  an  examination  of  the  tabulated  data  readily  discloses 
the  fact  that  many  of  them  show  taints  of  transfer  by  their 
range  of  hand  skill,  and  that  the  pure  left  hand  group  as  a 
whole  is  shown  by  the  skill  range  to  possess  the  transfer 
taint.  [Biervliet  evidently  saw  this  fact  for  he  says,  "Am- 
bidexters thus  appear  to  be  a  variety  of  left  men  with  great- 
er symmetry."] 

2.    Peg  Board  Data. 

The  summary  of  the  peg  board  tests  with  the  seventy- 
five  21-24  year  old  women  shows  (1)  that  the  25  pure  right 
handed  women  place  on  the  average  35.84  pegs  in  30  seconds 
with  the  right  hand,  and  30.64  with  the  left;  that  is,  they 
reveal  close  to  36  degree  (35.84  degree)  skill  with  the  right 
hand  and  close  to  31  degrees  (30.64  degree)  skill  with  the 
left;  (2)  that  the  25  pure  left  handed  women  place  on  the 
average  31.64  pegs  in  30  seconds  with  the  right  hand,  and 
36.04  pegs  with  the  left  hand ;  that  is,  they  reveal  close  to  32 
degree  skill  with  the  right  hand  and  36  degree  skill  with  the 
left  hand;  (3)  that  the  25  transferred  women  place  on  the 


70  A  STUDY  OF  HANDEDNESS 

average  33.04  pegs  with  the  major  hand,  and  31.60  pegs  with 
the  minor  hand ;  that  is,  they  show  33  degree  skill  with  the 
major  hand,  and  32  degree  skill  with  the  minor  hand.  These 
facts  undoubtedly  mean  what  was  found  true  in  the  shot 
tube  tests ;  namely,  that  the  pure  right  hander  and  the  pure 
left  hander  are  about  equal  in  major  and  minor  hand  skill, 
respectively,  but  that  the  transfer  falls  below  both  the  pure 
right  and  the  pure  left  hander  in  extreme  skill.  It  is  note- 
worthy, too,  that  in  spite  of  the  fact  that  the  pure  left  hand- 
ers  show  a  little  higher  average  skill  in  either  arm  than  is 
shown  by  the  pure  right  banders,  yet  we  find  a  lower  range 
of  skill  and  a  deviation  toward  the  transfer  type.  The  peg 
board  tests  with  the  three  hundred  50-60  year  old  men  show 
(1)  that  the  pure  right  banders  reveal  30  degree  skill  with 
the  right  hand,  and  26  degree  skill  with  the  left;  (2)  that 
the  pure  left  banders  reveal  close  to  27  degree  skill  with  the 
right  hand,  and  nearly  31  degree  skill  with  the  left;  and 
(3)  that  the  transfers  reveal  29  degree  skill  with  the  major 
hand,  and  27  degree  skill  with  the  minor  hand.  Here,  too, 
the  skill  ranges  show  that  both  the  pure  right  and  the  pure 
left  hander  reveal  a  major  hand  of  comparatively  extreme 
skill  and  a  minor  hand  of  comparatively  low  grade  skill, 
while  the  transfer  reveals  two  arms  of  about  equal  and  or- 
dinary sldll.  The  transfer  begins  to  appear  to  approxi- 
mate ambidexterity  without  extreme  skill.  Once  more  it  is 
noteworthy  in  passing  that  the  pure  left  hander,  in  spite 
of  the  fact  that  his  skill  in  placing  pegs  is  a  shade  superior 
to  that  of  the  pure  right  hander,  shows  the  same  lower  skill 
range  and  deviation  toward  the  transfer.  This  is  undoubt- 
edly further  evidence  of  transfer  taint. 

3.    Tapping  Rate  Data. 

The  summary  of  the  tapping  rate  tests  with,  seventy- 
five  7-9  year  old  girls  shows  (1)  that  the  25  pure  right 
handed  girls  reveal  143.68  degree  skill  with  the  right  arm, 
and  121.92  degree  skill  with  the  left  arm;  (2)  that  the  25 
pure  left  handed  girls  reveal  123.2  degree  skill  with  the 
right  arm,  and  141.64  degree  skill  with  the  left  arm;  (3) 
that  the  transfers  reveal  134.28  degree  skill  with  the  major 


A  STUDY  OF  HANDEDNESS  71 

arm,  and  126.64  degree  skill  with  the  minor  arm.  The  tap- 
ping rate  tests  with  the  three  hundred  30-40  year  old  wom- 
en show  (1)  204.4  degree  skill  in  the  right  arm  and  181.12 
degree  skill  in  the  left  arm  of  pure  right  handers,  (2) 
182.24  degree  skill  in  the  right  arm  and  201  degree  skill  in 
the  left  aiTu  of  the  pure  left  hander;  and  (3)  195.04  degree 
skill  in  the  major  arm  and  186.48  degree  skill  in  the  minor 
arm  of  the  transfers.  The  ranges  of  skill  for  the  two  arms 
reveal  once  more  that  the  pure  right  and  the  pure  left  hand- 
ers show  comparatively  high  grade  skill  in  the  major  arm 
and  comparatively  low  grade  skill  in  the  minor  arm,  while 
the  transfer  again  appears  to  approximate  ambidexterity, 
without  extreme  skill.  Taints  of  the  traditional  transfer 
ambition  of  the  race  are  again  evident  in  the  deviation  of 
the  pure  left  hander  toward  the  transfer  in  his  range  of 
skill. 

Division  of  Labor  in  Hand  Work. 

The  question  now  arises,  Is  the  workman  of  today 
better  equipped  with  two  equal  anus  of  ordinary  skill  or 
with  one  aim  of  high  grade  and  another  of  low  grade  skill  ? 
It  takes  but  a  httle  study  of  the  use  of  hands  and  arms  in 
the  skilled  labor  of  the  world  today  to  convince  the  honest 
inquirer  that  the  finest  skilled  labor  is  one  handed  skill. 
When  a  man  works  with  spade  or  shovel  or  pitchfork  or  hoe, 
it  ordinarily  make  httle  difference  whether  he  puts  the 
right  or  left  hand  forward,  since  the  labor  is  what  we  may 
call  rough  or  coarse  work,  dealing  with  relatively  inexact 
lines,  distances  and  quantities  that  are  not  measured  by  the 
micrometer  or  the  milligram.  The  ditcher  works  by  the 
rod,  the  shoveler  by  the  ton  or  by  the  hour,  the  haymaker 
thinks  in  terms  of  the  day  or  of  the  ton,  and  so  on.  The 
fact  is,  it  may  be  an  advantage  for  any  of  these  laborers 
to  work  first  right  or  left  handed  and  then  change.  Some 
degree  of  relief  or  rest  may  come  through  the  change  with- 
out loss,  and  perhaps  with  gain,  in  the  total  results.  But 
when  the  skilled  surgeon  removes  the  goiter  he  hardly 
trusts  the  knife  in  his  minor  hand  when  he  works  near  the 
carotid  artery  or  the  jugular  vein;  the  skilled  watchmaker 


72  A  STUDY  OF  HANDEDNESS 

w 

hardly  trusts  the  miniature  screwdriver  in  his  minor  hand  i 

when  he  seeks  to  adjust  the  microscopic  screw,  and  the 
skilled  draftsman  hardly  takes  his  pencil  in  his  minor  hand 
when  he  seeks  an  exact  termination  of  a  fine  line.  The 
fact  is,  skilled  labor  is  today  essentially  one  hand  skill,  and 
it  is  becoming  more  and  more  one  handed  in  the  degree  that 
heavy  labor  is  given  over  to  machinery  and  the  human 
hand  is  reserved  for  the  skillful  management  of  that  ma- 
chinery. The  finest  handwork  calls  for  one  highly  skilled 
working  hand  and  for  one  or  more  helping  or  holding  hands. 
Skilled  work  calls  for  brief  periods  or  moments  of  skill,  with 
pauses  liberally  interspersed  for  calculating  and  adjusting. 
Change  of  hands  could  hardly  relieve  the  skillful  workman^ 
since  it  is  not  the  moment  of  skilled  effort  that  wearies 
him,  but  rather  the  responsibility  of  reaching  fine  results, 
moment  by  moment;  and  this  could  not  be  relieved  by 
shifting  to  another  hand  controlled  by  the  same  brain. 
Then,  too,  extreme  skill  requires  continual  and  consistent 
exercise,  not  only  to  acquire  but  to  retain.  Finished  skill 
is  the  last  to  be  acquired  and  the  first  to  disappear.  Divi- 
sion of  labor  in  handwork  therefore  favors  hand  skill  by 
limiting  the  range  of  things  done  by  one  hand;  and  were 
we  bom  with  two  potentially  equal  arms,  or  even  with  four, 
it  were  still  prudent  to  train  each  hand  for  its  own  special 
work.  We  can  not  agree  with  Ballard  when  he  says  "there 
can  be  no  objection"  to  "a  more  even  distribution  of  dex- 
terities between  the  two  hands,"  even  though  he  makes 
"the  important  proviso  that  writing  should  always  be  done 
with  the  superior  hand."  (Jour,  of  Exp.  Ped.,  Vol.  L,  No. 
4,  p.  309.)  It  is  extreme  effort  along  with  extreme  guid- 
ance, extreme  circumspection,  that  wins;  and  the  total 
amount  of  exercise  required  to  sustain  a  given  grade  of  any 
given  hand  skill  in  one  hand  would  be  quite  inadequate  to 
maintain  that  hand  skill  if  divided  between  two  hands.  This 
study  shows  that  the  pure  right  hander  is  slightly  superior 
in  hand  skill  to  the  pure  left  hander,  tainted  with  ambidex- 
terity as  the  left  hander  commonly  is,  and  that  both  are 


A  STUDY  OF  HANDEDNESS  73 

clearly  superior  to  the  transfer,  *The  total  hand^  and  ai-m 
exercise  in  any  specific  line  of  activity  can  not  maintain  in 
two  hands  and  arms  the  same  high  pitch  of  skill  that  it  can 
maintain  in  one;  and  this  fact,  along  with  the  principle  of 
natural  selection  may  yet  be  made  to  account  for  the  fact 
that  the  race  is  unidextrous  and  not  ambidextrous.  (|This 
suggestion  agrees  with  the  theory  of  Dr.  Felix  Regnault.— 
Revue  Scientifque,  Paris,  June  13,  1914.) 

In  the  world  of  skilled  labor,  therefore,  the  transfer  is 
at  a  disadvantage.  He  can  not  hope  to  compete  with  the 
extreme  skill  of  either  the  pure  right  or  the  pure  left  hand- 
er;  and  the  parent  or  teacher  who  assumes  to  follow  tra- 
dition in  transferring  the  bom  left  handed  child,  must  also 
assume  the  responsibility  for  crippling  him  in  the  v/orld 
of  skilled  labor.  Some  ambidexters  show  considerable  skill 
in  some  forms  of  labor,  but  this  only  suggests  what  these 
same  individuals  might  have  accomplished  had  they  been 
permitted  fully  to  develop  their  major  arm  potentialities. 

We  are  then  driven  to  believe  that  it  is  a  bad  tradition 
that  shifts  the  born  left  handed  child  to  the  right  hand, 
for  at  least  two  reasons;  namely,  (1)  it  endangers  his^ 
speech,  and  (2)  it  cripples  his  hand  and  arm  skill ;  and  the 
fact  that  so  many  children  are  transferred  by  accident  (1% 
of  both  right  handers  and  left  handers),  many  of  these  in 
turn  being  unknown  until  revealed  by  arm  measures,  gives 
sufficient  ground  for  the  conviction  that  every  child  should 
be  measured  early  in  life  to  give  assurance  of  his  birthright 
of  hands.  Such  a  routine  procedure  would  make  it  possible 
to  preclude  all  hand  transference  excepting  such  as  may 
be  unavoidably  due  to  incapacitation  of  hand  or  arm  or 
tongue  (aphasia),  through  injury  or  disease. 


*  A  little  study  of  the  data  will  show  that  the  average  skill  of  the 
two  hands  and  arms  of  the  transfer  is  but  little  less  than  the  average 
skill  of  the  two  hands  and  arms  of  the  pure  right  or  of  the  pure  left 
hander,  but  his  division  of  labor  between  the  two  hands  is  undoubtedly 
responsible  for  the  fact  that  he  lacks  extreme  skill. 


CONCLUSIONS. 

Based  on  the  data  of  this  study,  we  may  draw  the  fol- 
lowing conclusions: 

1.  The  human  being  is  bom  with  a  major  and  a  minor 
hand  and  arm.  96%  of  the  race  are  born  right  handed,  and 
4%  left  handed. 

2.  Bom  handedness  is  revealed  by  the  bones  of  the 
arm — the  major  arm  having  the  more  massive  bone  equip- 
ment— and  this  evidence  is  present  at  birth. 

3.  The  most  convenient  measures  for  determining 
bom  handedness  are — 

1.  The  length  of  the  ulna  plus  (ulna  plus  hand  to 
middle       knuckle  of  little  finger) . 

2.  The  circumference  of  the  palm. 

3.  The  circumference  of  the  wrist. 

4.  The  length  of  the  humerus. 

4.  Adopted  handedness  is  revealed  by  the  muscle 
swells  of  the  arm — the  adopted,  or  preferred,  arm  having 
the  higher  per  cent  of  swell. 

5.  The  most  convenient  measures  for  detemiining 
adopted  handedness  are — 

1.  The  circumference  of  the  relaxed  forearm  taken 
within  the  zone  of  maximum  swell. 

2.  The  circumference    of    the    contracted  forearm 
taken  within  the  zone  of  maximum  swell. 

3.  The  circumference  of  the    relaxed    ami    taken 
within  the  zone  of  maximum  swell  of  the  biceps. 

4.  The  circumference  of  the  contracted  arm  taken 
within  the  zone  of  maximum  swell  of  the  biceps. 

(The  difference  between  the  relaxed  and  contracted 
measures  of  any  muscle,  divided  by  the  relaxed  measure, 
gives  the  percentage  of  swell.) 

6.  Transferred  handedness  may  be  found  by  compar- 
ing the  bone  measures  of  the  arm  and  hand  with  the  mus- 
cle swell  measures  of  the  ami.    A  born  right  hander  who 


A  STUDY  OF  HANDEDNESS  75 

has  adopted  the  left  hajid,  or  a  born  left  hander  who  has 
adopted  the  right  hand,  is  transferred. 

7.  Three-fourths  of  all  born  left  handers  are  trans- 
ferred to  the  right  hand,  either  by  accident  or  by  purposive 
interference.  Approximately  1%  of  either  born  right  or 
bom  left  handers  are  transferred  by  accident.  One  indi- 
vidual out  of  about  25  adopts  the  potentiality  minor  arm, 

8.  Physiological  disaster  in  the  form  of  stammering 
is  imminent  in  hand  transference.  One-third  of  all  left-to- 
right  transfers  and  one-sixth  of  all  right-to-left  transfers 
are  afflicted  with  stammering,  as  against  approximately 
1%  of  all  pure  left  handers  (tainted  or  untainted  with  trans- 
fer tradition)  and  less  than  1%  of  all  pure  right  handers. 

9.  Stammering  is  intimately  associated  with  writing 
with  the  potentially  minor  hand,  and  the  traditional  trans- 
fer of  the  left  handed  child  to  his  right  hand  in  writing  is 
to  be  condemned  as  unwarranted  and  dangerous  interfer- 
ence. 

10.  The  pure  right  hander  reveals  about  the  same  de- 
gree of  hand  skill  as  the  pure  left  hander  who  has  not  been 
interfered  with  in  the  free  use  of  his  left  hand;  but  the 
transfer  lacks  the  extreme  skill  of  the  pure  right  and  of 
the  pure  left  hander,  and  he  can  not  hope  to  compete  suc- 
cessfully with  the  pure  handed  in  the  skilled  labor  of  the 
world.  The  transfer  has  two  ordinary  aiTns  rather  than 
one  skilled  and  one  helping  arm. 

11.  The  ambidexter  is  a  transfer,  or  near  transfer, 
either  from  left  to  right  or  from  right  to  left.  The  more 
marked  the  general  ambidexterity,  the  nearer  the  individ- 
ual is  to  the  neutral  line  of  hand-skill  variation,  and  the 
lower  the  range  of  skill. 

12.  The  evidence  of  born  handedness  is  present  at 
birth;  hence  it  is  possible  to  measure  the  child  for  born 
handedness  early  in  life  and  so  prevent  any  hand  transfer- 
ence except  such  as  may  be  necessitated  by  injury  or  dis- 
ease. 


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